The purpose of this study is to determine how the body uses glycerol during fasting. The specific aims are: 1) determine whether the uptake of FFA relative to glycerol in the splanchnic and renal beds during fasting are consistent with the need for systemic FFA re-esterification; 2) assess the contribution of splanchnic adipose tissue lipolysis to systemic FFA availability during fasting; and 3) examine whether glycerol used by the liver to synthesize VLDL triglyceride originates from a common intrahepatic gluconeogenic precursor pool or from circulating free glycerol. Four volunteers have been included in this study. Glycerol turnover and the incorporation of glycerol into the backbone of VLDL triglyceride was measured in these four volunteers. As part of the study the volunteers received deuterated water in order to examine the incorporation of deuterium into the glycerol and glucose in plasma. These samples were sent to Dr. Bernard Landau at Case Western Reserve. We have completed the glycerol analysis at Mayo.